1. Field of the Invention
This invention relates to the use of organo-silanes as mold release agents. More particularly, it refers to aqueous compositions and methods of using select organo-silanes for coating mold surfaces and thereafter obtaining clean mold surfaces after repeated ejections of plastic parts from the mold.
2. Description of Prior Art
In the process of preparing molded products such as urethanes, natural rubber, silicones, neoprene, and other synthetic elastomers, it is necessary to coat the core surfaces of a mold to prevent the molded product from sticking to the mold. Coatings used to prevent such molded products from sticking to molds are called mold release agents. Most prior art mold release agents were organic solvent based compositions. This caused undesirable vapors dangerous to the environment and particularly to the mold operators.
An advance in non-solvent based mold release agents was disclosed in U.S. Pat. No. 5,219,925. Methyltriethoxysilane, methyltrimethoxysilane, vinyltriethoxysilane and vinyltrimethoxysilane were each disclosed as an active component in an aqueous mold release composition. These compositions have been readily accepted in the marketplace and one or more is used in mold release compositions commercially. One is identified as CRYSTAL.RTM. 1053, containing methyltriethoxysilane. Although these compositions are ideal for use in repeated mold releases of plastic products and elastomers, the molds themselves have sometimes become discolored. Another composition that will have satisfactory mold release properties and prevent mold discoloration is needed.